Spiropyran compounds are most well-known as typical organic compounds which reversibly colors or decolorizes upon exposure to the energy of light or heat. Examples and properties of these derivatives are collectively described, for example, in G. H. Brown, "Photochromism" (John Wiley & Sons, Inc., 1971). Spiropyran compounds have an asymmetric center on a spirocarbon. However, all conventional spiropyran compounds are perfect racemic modifications having an optical purity of 0%, and optically active spiropyran compounds which exhibit specific properties of optical active substances such as optical rotation have never been obtained.
The present inventors have studied intensively in order to solve the above problem of the prior art. That is, an object of the present invention is to provide spiropyran compounds and optically active spiropyran compounds and their use.